A fuel injector of an internal combustion engine is affected by wear, environmental conditions, and other factors. When a fuel injector is initially tested and assembled into an internal combustion engine, a control system of the engine is provided with calibration values that provide for optimal operation of the fuel injector, such as the amount of fuel delivered for an injector on-time. As the fuel injector's performance changes with time, the original calibration values may lead to less than optimal performance for the fuel injector.